JP2011093249A - Wooden spring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wooden spring retaining flexibility in a dry state. <P>SOLUTION: The wooden spring has a body 2 comprising a square timber and a plurality of cantilevers 4 made of a slit 3 prepared in the body 2. The slit 3 consists of a plurality of first slits 3A which are formed in a longitudinal direction caving from one side surface of the body 2 into inside and second slits 3B which are formed between the first slits 3A from another side surface facing the one side surface toward the inside. Width of the slit 3 is set within allowable flexure rate of the cantilever 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wooden spring.

  As a conventional wooden spring, a wooden strip spring using a strip bent in a loose arc shape is disclosed (for example, Patent Document 1). This wooden strip spring can be used for a bed floor or a chair seat.

  In this way, wood and bamboo can be used as materials for houses and furniture with slight processing. In general, wood is used by drying in order to improve strength characteristics and prevent decay due to high humidity.

  While wood has improved strength properties due to drying, there is a problem that the inherent flexibility is lost. In the case of conventional wood, when a deformation such as “twist”, “bend”, and “shrink” is given, it is common to soften the wood material by adding moisture and heat.

JP 2006-149948 A

  Since wood is fixed in a deformed state after the loss of moisture and heat, it can be processed for the purpose of fixing the deformed state, but it is always twisted, bent or shrunk. There is no wood with such flexibility.

  Accordingly, an object of the present invention is to provide a wooden spring having flexibility.

  According to a first aspect of the present invention, a main body made of square material and a plurality of slits formed by cutting out side surfaces of the main body in a direction substantially orthogonal to the longitudinal direction of the main body are formed and connected in the longitudinal direction of the main body A plurality of cantilever portions.

  The invention according to claim 2 of the present invention is characterized in that the slit includes a plurality of first slits formed from one side surface of the main body toward the inside, and the other side surface facing the one side surface toward the inside. It is characterized by comprising a second slit formed one by one between one slit.

  The invention according to claim 3 of the present invention is characterized in that a width of the slit is formed to be equal to or less than an allowable deflection amount of the cantilever portion.

  The invention according to claim 4 of the present invention is characterized in that the bottom surface of the slit is formed in a curved shape.

  According to the present invention, the wooden spring can have flexibility even in a dried state, so that a spring that behaves elastically against an external force can be obtained.

It is a perspective view which shows the whole structure of the wooden springs concerning this invention. It is a partial expansion perspective view which shows the structure of a cantilever. It is a model figure which shows the mode of bending of a cantilever beam. It is a graph which shows the relationship between the slit depth and slit width in a cantilever part. It is a graph which shows the relationship between the slit width and material thickness in a cantilever part. It is a graph which shows the relationship between the material thickness and slit depth in a cantilever part. It is a graph which shows the view of the setting method of a slit width. It is a load-deflection curve which shows the result of having repeatedly performed the load test in the wooden spring.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A wooden spring 1 shown in FIG. 1 has a plurality of cantilever portions 4 formed by a main body 2 made of square wood and a plurality of slits 3 formed in the main body 2. The material of the wooden spring 1 is not particularly limited, and for example, solid wood such as oak, cypress, cedar or drill can be used as wood.

  The slit 3 is formed in a direction orthogonal to the longitudinal direction. The slit 3 includes a first slit 3A formed uniformly in the longitudinal direction from one side surface 2A of the main body 2 toward the inside, and the first slit 3A from the other side surface 2B facing the one side surface 2A toward the inside. The second slits 3B are formed one by one between each other.

  Thereby, the slit 3 is formed with the first slit 3 </ b> A and the second slit 3 </ b> B alternately over the entire body 2. The slit 3 has a depth (hereinafter referred to as “slit depth”) L that is more than half of the length x between the side surfaces formed by the one side surface 2A and the other side surface 2B of the main body 2. Is formed.

  By the slit 3, a plurality of cantilever portions 4 are formed in the main body 2 so as to be connected in the longitudinal direction. Each cantilever part 4 has a beam part and a connection part. In the case of this embodiment, the first beam portion 5A, the second beam portion 5B, the third beam portion 5C,... The first beam portion 5 </ b> A and the second beam portion 5 </ b> B are integrally connected by a first connection portion 6 on the other side surface 2 </ b> B of the main body 2. The second connection portion and the third connection portion are integrally connected to each other at the second connection portion 7 on one side surface 2A of the main body 2.

  In this way, the wooden spring 1 is formed by integrally connecting 18 beam portions as a whole by 17 connection portions and integrating the cantilever beam portion 4.

  Next, the setting method of each part in the wooden spring 1 will be described. In the following description, the case where the wooden spring 1 receives a compressive load from the upper and lower surfaces will be considered. Further, as shown in FIG. 2, one cantilever portion 4 is considered as a minimum unit. Since all the structures of the cantilever beam portion 4 are the same, in the following description, a combination of the first beam portion 5A and the first connection portion 6 will be described.

  The width of the main body 2 is bmm, the slit depth is Lmm, the slit width is tmm, and the height (material thickness) of the first beam portion 5A is hmm. When a load of P (N) is applied to the tip of the first beam portion 5A, the first beam portion 5A cannot bend beyond the slit width tmm even if it is not bent and broken.

  In other words, by making the slit width t equal to or less than the allowable deflection amount, it is possible to prevent the wooden spring 1 from being broken. Furthermore, if the deformation of the first beam portion 5A is limited to the elastic deformation region, the load response due to the repeated load becomes constant, and a mechanism similar to that of the metal spring can be obtained.

  When the elastic modulus E is set and the first beam portion 5A receives the concentrated load P at the tip, the deflection (FIG. 3) δ is expressed by the following equation (1).

  Further, the bending strength σ at that time is expressed by the following equation (2).

  When the above formulas 1 and 2 are put together, the following formula 3 is obtained.

  When the bending strength σ and the elastic modulus E are known, the right side of Equation 3 is a constant k, and Equation 3 is expressed by Equations 4, 5, and 6 with h, δ, and L as variables.

Here, if the deflection δ is regarded as the slit width t, and k / h, kL ² , and δ / k are constants in each of the equations (4), (5), and (6), The relationship between width t (Fig. 4), Equation 5 is expressed as the relationship between slit width t and material thickness h (Fig. 5), and Equation 6 is expressed as the relationship between material thickness h and slit depth L (Fig. 6). The

  Consider the definition of slit depth L and slit width t in Equation 4 with reference to FIG. In the case of the slit depth L1, the amount of deflection is t1, and by making the slit width t equal to or less than t1, the first beam portion 5A is not broken by the load P and can be used as the wooden spring 1.

  The result of the preliminary experiment using white oak is shown.

  It is assumed that the wooden spring 1 is manufactured with the specifications of an elastic modulus E of 1 GPa, a bending strength of 24 MPa, a main body width b = 35 mm, and a material thickness h = 4 mm. In this case, a sample having a slit depth L of 30 mm and a slit width t of 3 mm was prepared based on the values L = 30 mm and δ = 3.6 mm obtained from Equation 4. Here, the reason why the slit width t is set to 3 mm is to keep the deflection amount at a proportional limit.

  Using this sample, the load sag curve shown in FIG. 8 was obtained by repeating the load six times with the maximum deflection δ of the cantilever 4 being 3 mm. The deformation speed was (5 mm / min). From this figure, it can be seen that the load curve in the repetition keeps linearity and has reproducibility, so that the cantilever portion 4 repeats elastic deformation.

  As described above, in the wooden spring 1, the elastic modulus E, the bending strength σ of the main body 2, the height (material thickness) h of the first beam portion 5A, the slit depth L, the slit width t (allowable deflection amount). δ) is closely involved, and it can function effectively as a spring by producing a material with specifications satisfying the following inequalities (7), (8), and (9).

  Next, the operation and effect of the wooden spring 1 will be described.

  First, a case where a load is applied in the longitudinal direction to the vertically-oriented wooden spring 1 will be described. When a downward load (compressive load) in the longitudinal direction is applied from the upper surface of the first beam portion 5A to the vertically-arranged wooden spring 1, the first beam portion 5A is connected to the first connection portion by the load. 6 is elastically deformed around the center of rotation. At the same time, the load is transmitted from the first connection portion 6 to the second beam portion 5B, so that the second beam portion 5B is elastically deformed with the second connection portion as a rotation center.

  In this manner, the load is sequentially transmitted from the third beam portion 5C to the further lower beam portion via the connection portion, and each beam portion is elastically deformed with each connection portion as a rotation center. Thereby, the wooden spring 1 absorbs the load as a whole and contracts.

  Similarly, when an upward load (tensile load) in the longitudinal direction is applied to the upper surface of the first beam portion 5A of the wooden spring 1, each beam portion has each connection portion as the center of rotation as described above. Elastically deforms. Thereby, the wooden spring 1 absorbs the load as a whole and extends.

  Next, a case where a load (bending load) is applied in a direction perpendicular to the longitudinal direction to the vertically-made wooden spring 1 will be described. Even when a load is applied to the first beam portion 5A of the wooden spring 1 with the lower surface fixed in a direction orthogonal to the longitudinal direction, that is, in the lateral direction, each beam portion is connected to each connection portion in the same manner as described above. Elastically deforms as the center of rotation. Thereby, the wooden spring 1 absorbs the load as a whole and bends and deforms in the direction of the load around the lower end.

  As described above, the wooden spring 1 can be flexible even in a dried state, and thus a spring (member) that behaves elastically against an external force can be obtained.

  Since the wooden spring 1 can form the cantilever portion 4 by forming a plurality of slits 3, it can be easily formed with only a tool such as a saw, without requiring complicated processing. .

  Moreover, since the wooden spring 1 integrally connects the plurality of cantilever portions 4 in the longitudinal direction, the total amount of deflection as a whole can be increased. Therefore, the wooden spring 1 can easily set desired flexibility.

  The wood spring 1 can be variously changed in characteristics by appropriately selecting the shape of the slit 3, for example, the slit width t, the slit depth L, and the height (material thickness) h of the beam portion 5. Therefore, desired characteristics can be easily obtained.

  Further, the wooden spring 1 is set so that the slit width t is equal to or less than the allowable deflection amount δ, so that the beam portion 5 comes into contact within the elastic deformation region and can be prevented from being damaged. Therefore, since the wooden spring 1 can be used in the elastic deformation region, durability can be improved.

  Further, the wood spring 1 is formed so that the slit depth L is more than half of the length x between the side surfaces formed by the one side surface 2A of the main body 2 and the other side surface 2B. It is possible to have flexibility more reliably.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention. For example, in FIG. 1, the bottom of the slit 3 is illustrated as a flat surface. However, the present invention is not limited to this, and the bottom surface of the slit 3 may be curved, for example, semicircular. By making the bottom surface of the slit 3 curved, stress concentration in the portion can be prevented. Therefore, the wooden spring 1 can further improve the durability.

  Moreover, although the slit 3 was arrange | positioned equally and the slit width t was all set to the same length in the said embodiment, this invention is not limited to this, The slit 3 is made non-uniform | heterogenous. The slits 3 having different slit widths t may be provided in the single main body 2.

  Moreover, in the said embodiment, the slit 3 is formed in the direction orthogonal to a longitudinal direction, The 1st slit 3A formed in the longitudinal direction equally from the one side surface 2A of the main body 2 toward the inside, and the said one Although a case has been described in which the second slit 3B is formed between the first slits 3A from the other side 2B facing the side 2A to the inside, the present invention is not limited thereto. .

  For example, although not shown, the first slit and the second slit are provided to form the first cantilever part in a certain range in the longitudinal direction of the main body, and each side surface is 90 degrees out of phase with the other side surface. It is good also as providing the 3rd slit and the 4th slit, and forming the 2nd cantilever part in which a 90 degree phase differs from the 1st cantilever part outside the above-mentioned fixed range. As described above, by appropriately providing the slit 3 on the desired side surface of the main body 2, the main body 2 can be more complicatedly deformed, so that the wood spring 1 having more flexible flexibility can be obtained.

  In this case, even when loads in two directions orthogonal to the longitudinal direction are simultaneously applied, bending can be performed in the two directions.

  The wood spring 1 has been described as a case where 18 beam portions are integrally connected by 17 connection portions as a whole. However, the present invention is not limited to this, and the number of beam portions and connection portions is not limited. Can be changed as appropriate.

  In the above-described embodiment, the wooden spring 1 has been described for the case where a solid material is used as wood. However, the present invention is not limited to this, and plywood, laminated material, particle board, MDF, WPC (wood / plastic composite material). It is also possible to use wood materials such as. In this case, the slit 3 can also be formed by press molding or die molding (injection molding or extrusion molding).

  The present invention has deformation performance, shock absorption, and design, and can be used as furniture, interior goods, and shock absorbers.

DESCRIPTION OF SYMBOLS 1 Wood spring 2 Main body 2A One side 2B Other side 3 Slit 3A 1st slit 3B 2nd slit 4 Cantilever part
b Width δ Deflection

Claims (4)

A body made of square wood,
A wood having a plurality of slits formed by cutting out side surfaces of the main body in a direction substantially perpendicular to the longitudinal direction of the main body, and a plurality of cantilever portions connected in the longitudinal direction of the main body. Spring made. The slit is
A plurality of first slits formed from one side of the main body toward the inside;
2. The wooden spring according to claim 1, wherein the spring is made of a second slit formed one by one between the first slits from the other side facing the one side toward the inside.   3. The wooden spring according to claim 1, wherein a width of the slit is less than an allowable deflection amount of the cantilever portion.   The wooden spring according to any one of claims 1 to 3, wherein a bottom surface of the slit is formed in a curved shape.

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